A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
Dear Ray.ME,
Good day! Thank you for posting in Microsoft Community. We are happy to help you.
We went through the post carefully. When testing from our side, we can reproduce the same behavior that the "Shared with us" tab is not showing in SharePoint sites.
Per searching, we found other users also noticed this same behavior in SharePoint and they found a workaround as following:
Firstly open the document library in the site and add "?view=3" to the library URL, then the URL will be like:
https://tenant.sharepoint.com/sites/sitename/Shared%20Documents/Forms/AllItems.aspx?view=3
It shows Shared With Us in modern experience.
Then you can add this link of "Shared with us" to the left navigation menu with steps below:
Click Edit from left navigation, then click the plus + icon, choose an option Link, enter the URL we mentioned above into Address box and click OK and then Save.
After that, clicking the link from left navigation menu will take you to Shared With Us page in modern experience.
Hope above can help you!
At the same time, we know it would be definitely ideal if the "Shared with us" tab can show in SharePoint site, thank you for bringing thing to our attention. We sincerely recommend you vote for this similar idea in SharePoint Feedback Community: bring back the "shared with us" feature in SharePoint · Community (microsoft.com) Our Product Team is in-charge of the site and they are constantly checking the comments and feedback from our customers. Thank you for your cooperation and understanding!
Hope you keep safe and healthy always!
Sincerely,
Tina | Microsoft Community Moderator